Treaty interruption between Number 13 and Yamato

Number 13 was a design step toward Yamato, although the classes differed in many respects. Yamato came after roughly two decades in which naval treaties curtailed Japan's capital-ship construction, so the earlier project reveals a different evolutionary path. Japan was already preparing to build Number 13 at Yokosuka Naval Arsenal, Mitsubishi's Nagasaki yard, and Kawasaki's Kobe yard. Yamato combined the same shaft horsepower with greater displacement, a hull roughly 11 metres shorter, about 8 metres more beam, and deeper draft. Those proportions mattered because machinery, hull form, and yard capacity shaped operational capability alongside headline gun calibre.